Thinning on the Angeles National Forest> > "Ian St. John" <firstname.lastname@example.org> wrote in message
Ian St. John
istjohn at noemail.ca
Tue Feb 24 12:49:40 EST 2004
"Bob Weinberger" <bobsstuff at verizon.invalid.net> wrote in message
news:LqD_b.2286$921.1112 at nwrddc02.gnilink.net...
> "Ian St. John" <istjohn at noemail.ca> wrote in message
> news:T1x_b.5089$253.524315 at news20.bellglobal.com...
> > It isn't that close. Obviously the land is grouped into denser and less
> > dense stands but that doesn't obviate the metric. Overall, the SDI is
> > low, and this calculation was for 'mixed size average', which is still
> > ( according to the documentation ). It may not be as precise as a region
> > region assessment but it still give a 'rough estimate' of the stocking
> > levels overall.
> The above is a prime example of your lack of familiarity with conditions
> the PP region leading to faulty reasoning and conclusions. Of what use is
> "rough estimate of the stocking level overall" for determining whether
> trees are likely to be under stress on specific sites, in an area where
> stocking is extremely clumpy and variable - the normal condition in many
I am making up for the fact that you have been unable to support any claims
on the specific site. As I can only find a report on the general condtion in
the Kaibab, I looked at the metric for general stocking levels, not specific
areas of overstocking. I am still waiting for you to supply some facts that
can justify the level of timber removal that is being done, but you fail
each and every time to justify your claims.
> > The 'SDI' maximum on which the 'fully occupied' is based is 35 of
> > stand density and that has been documented as 800 for Ponderosa Pine. As
> > have not given a basis for the SDI being any different in this neck of
> > woods, your claims of superior knowledge ( aka argument by authority )
> > dismissed for the fool bait they are.
> > > Depending on the specific site
> > > productivity- which varies greatly from site to site, often in very
> > > gegraphic distances - a fully occupied PP stand my have as many as
> > > 3-5" TPA or as few as 30 10-15" TPA. On many of the lower PP sites
> > > crown coverage is all the site can support.
> > SDI is a metric that is independent of the dbh. That is why it is used.
> > really ought to take forestry 101 if you don't even know that much! The
> > smaller the tree the smaller the basal area and therefore the larger the
> > number of trees for the same SDI. That is why your piece above is
> > is just an expansion of the SDI for different average dbh levels, but
> > not say that the SDI would be any different.
> Congratulations, you have apparently learned a new term. Now if you only
> learned how to calculate SDI, and how to apply it properly you might start
> to understand what I am talking about.
All of my calculations are from papers on the subject. They are NOT my
invention and I checked at more than one site to ensure that the
calculations were accurate.
> SDI is a measure to be used to
> determine the level of inter - tree competition for a specific species ON
> SPECIFIC SITE PRODUCTIVITY CLASS.
Site productivity class is merely a measure of the cubic meters of wood
added to a natural stand per year. It does not equate to, or limit stocking
levels which are more about the amount of trees stocked. The *rate* of
growth is NOT fixed and so there is some difference between the two metrics.
I see that you are focussed on the primary metric of the Timber Indusstry,
which is the rate of growth of extractable timber... ( i.e. the productivity
index ) not the health of the forest as a forest.
> It is NOT a measure to be used to
> determine the stockability of a specific site. A maximum SDI ( or a Max.
> fo that matter) only has relevance for a specific site productivity class.
"Stocking is an expression of the extent to which *growing space* is
effectively utilized by live trees."
"Stand density index-Many factors influence the rate at which trees grow and
thrive, or die. As tree size and density increase, competition for available
resources increases. Stand density index (SDI), as developed by Reineke
(1933) is a relative measure quantifying the relationship between trees per
acre, stand basal area, average stand diameter, and stocking of a forested
stand. The concept was developed for even-aged stands, but can also be
applied to uneven-aged stands (Long and Daniel 1990; see next paragraph for
an explanation of even-aged and uneven-aged stands). SDI is usually
presented as a percentage of the maximum SDI for each forest type (USDA
1991). SDI was computed for each location using those maximums, and the
results were grouped into six classes (fig. 8). A site is considered to be
fully occupied at 35 percent of SDI maximum, which marks the onset of
competition-related stresses and slowed growth rates (USDA 1991). Based on
FIA sample data, 50 percent of all forest stands in the Kaibab National
Forest are considered to be fully occupied."
The productivity index is only a metric for optimizing tree farms for lumber
production. The focus of your work is thus revealed. It is unfortunate that
you want to apply such metrics, designed for trees as timber crops, to
'preserving natural forests'
> If a maximum SDI for a species across its entire range is stated, it is
> a measure of the maximum that species can reach on the best sites it can
I can find no reference to SDI vs 'productity class'. It must be something
unique to timber companies...and their paid 'consultants'.
> Secondly, despite the fact that I may have confused you by using stands
> 2 different quadratic mean diameters, if you knew how to calculate SDI,
> would have quickly determined that the SDI of the first stand ( 600TPA
> an assumed QMD of ~ 4") has an SDI over 4 times that of the second stand
> (30 TPA with an assumed QMD of ~ 12"). In any case comparing the SDI's of
> the two stands is irrelevant, since the examples were given to illustrate
> that they can both represent fully occupied conditions for the sites they
> are on.
As I said, the SDI measures the stand densitiy irregardless of size class.
Of *course* many more small trees can occupy an acre. It is a trivialisation
that doesn't need to be calculated out. It is equivalent to someone giviing
a formula and then you posting several calculations of the formula as
'rebuttal' which it does not do.
> The above is not "argument by authority" since you can verify it by
> retaking Forestry 101 or at least doing a little more thorough reading of
> Dr. Reineke's treatment of the concept.
No. It is not argument by authority. It is basically the 'big lie' where you
post something that is true but irrelevant as a 'rebuttal' and then claim
that you have shown an error. Most people will believe the one claiming the
authority just because he claims the authority without looking to see. The
fact is that SDI gives the numbers you post! You have done NOTHING to make a
case for the thinning proposed in the Kaibab North Rim.
You see incapable of supporting the logging proposed on the Kaibab and so
this is not a useful thread. As I said, unless you can start supporting your
claims, you are wasting everyones time with the distortions and misdirection
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